From: "Dan Minette"
> I'm going to focus on one aspect of Robert Shaw comments for the moment.
> >
> > There isn't room in physics for new stuff on a scale that affects the
> > workings of the brain. Penrose appeals to nonlinearities in quantum
> > theory connected with gravity but there is no independant evidence
> > of such effects. Quantum gravity is even less likely to be relevant.
> >
>
> Actually, there might be room in mesoscopic physics. I'm not counting on
> this room for my answer, but its still worth noting. Mesoscopic physics
is
> probably the most likely area for something fundamentally new and usable
to
> be found in physics. Quantum gravity will be new, but it probably will
not
> have applications.
Mescopic physics is fully reducable to microscopic physics and ultimately
the standard model.
>
> > It's not possible in practice but proving it impossible in princple is
> > much harder. You need to discover new physics which has a significant
> > effect on processes at the energy levels and time scales found in the
> brain.
>
> No, all I have to do is show that quantum chaos is involved.
That isn't sufficient. Chaos isn't unpredictable, just exponentially
harder to predict than linear systems.
A chaotic physical system, whether classical or quantum, is
still going to be simulatable to arbitary accuracy by a
Turing machine, just not in polynomial time. That means such
systems can't do non-algorithmic processes.
>
> > In known physics the movement of the human brain through its infinite
> > dimensional phase space can be precisely predicted by using the
> > Hamiltonian operater.
>
> I would like to see that worked out. If it is true, I'd be very
surprised.
If it isn't true, then classical quantum physics is false.
> Think about perfect billiard balls on a perfect table traveling at 10
meters
> per second and intereacting (on average) every meter. Quantum chaos is
> involved in their position within 1 second.
>
Such chaos is only a practical barrier to predictability, not a theoretical
barrier.
By definition, H|Universe>=i(d/dt)|Universe>, barring quantum gravitational
effects.
If you specify H, how the energy of the universe depends on its states, the
time evolution of the universe is fully determined.
It's not practical to specify H that precisely, but it is possible in
principle.
The mere existence of a algorithm that can simulate the universe to arbitary
accuracy is enough to imply that nothing within the universe can perform
any non-algorithmic procedure, even if the universe simulating algorithm is
neither constructable nor executable within the universe being simulated.
--
Robert
